U.S. patent application number 09/873455 was filed with the patent office on 2002-06-06 for method for producing a fluid device, fluid device and analysis apparatus.
Invention is credited to Frech, Johannes, Mueller, Martin, Nommensen, Peter, Staehler, Cord F., Strobelt, Tilo.
Application Number | 20020068021 09/873455 |
Document ID | / |
Family ID | 7665876 |
Filed Date | 2002-06-06 |
United States Patent
Application |
20020068021 |
Kind Code |
A1 |
Staehler, Cord F. ; et
al. |
June 6, 2002 |
Method for producing a fluid device, fluid device and analysis
apparatus
Abstract
In the case of a method for producing a fluid device with a
fluid structure having an active height, a basic wafer is provided,
which comprises a supporting substrate, an insulating layer on the
supporting substrate and a patterned layer on the supporting
substrate, the thickness of the patterned layer determining the
active height of the fluid structure. Following this, the fluid
structure is produced in the patterned layer of the basic wafer,
said fluid structure extending through the semiconductor layer. A
transparent wafer is then applied so that the fluid structure is
covered. Subsequently, the supporting substrate and the insulating
layer are removed from the back so that the fluid structure is
exposed at a second surface of the patterned layer. Finally, a
second transparent wafer is attached to the exposed second surface
of the semiconductor layer so that the fluid structure is covered.
The essential parameter of the fluid device, viz. the active height
of the fluid structure, need no longer be controlled making use of
the etching parameters, but is already determined by the
specifications of the starting material, e.g. an SOI wafer. This
means that economy-priced fluid devices can be produced with high
precision.
Inventors: |
Staehler, Cord F.;
(Weinheim, DE) ; Strobelt, Tilo;
(Villingen-Schwenningen, DE) ; Frech, Johannes;
(Trossingen, DE) ; Nommensen, Peter;
(Villingen-Schwenningen, DE) ; Mueller, Martin;
(Dietingen, DE) |
Correspondence
Address: |
GLENN PATENT GROUP
3475 EDISON WAY
SUITE L
MENLO PARK
CA
94025
US
|
Family ID: |
7665876 |
Appl. No.: |
09/873455 |
Filed: |
June 4, 2001 |
Current U.S.
Class: |
422/504 ;
204/601; 216/2; 422/82.05 |
Current CPC
Class: |
B81B 2203/0338 20130101;
Y10T 436/25 20150115; B01L 3/502707 20130101; B81B 1/00 20130101;
Y10T 436/11 20150115; B81C 1/00119 20130101; B01L 2200/12 20130101;
Y10T 436/2575 20150115; B81B 2201/058 20130101; B81C 2201/019
20130101; B81C 1/00357 20130101 |
Class at
Publication: |
422/100 ; 216/2;
204/601; 422/82.05 |
International
Class: |
B01L 003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 5, 2000 |
DE |
10060433.1 |
Claims
1. A method of producing a fluid device with a fluid structure
having an active height, said method comprising the following
steps: providing a basic wafer comprising a supporting substrate,
an intermediate layer on the supporting substrate and a patterned
layer on the supporting substrate, the thickness of the patterned
layer determining the active height of the fluid structure, said
intermediate layer being of such a nature that it is essentially
not impaired by a patterning of the patterned layer; patterning the
patterned layer so as to produce the fluid structure of the fluid
device, the fluid structure extending from a first surface of the
patterned layer to the intermediate layer; attaching a first
transparent wafer so that the fluid structure is covered; removing
the supporting substrate and the intermediate layer so that the
fluid structure is exposed at a second surface of the patterned
layer; and attaching a second transparent wafer so that the fluid
structure is covered.
2. A method according to claim 1, wherein the basic wafer is an SOI
structure comprising a supporting wafer of silicon, an insulating
layer of oxide as an intermediate layer and a silicon layer as a
patterned layer on the oxide layer.
3. A method according to claim 2, wherein the patterning step is
carried out by means of dry etching silicon, the oxide layer acting
as an etch stop.
4. A method according to claim 1, wherein the first transparent
wafer is a glass wafer which is attached to the patterned layer by
means of anodic bonding.
5. A method according to claim 1, wherein the fluid structure is
passivated by means of an oxide layer prior to the step of
attaching the first transparent wafer.
6. A method according to claim 1, wherein the second transparent
wafer is a glass wafer which is attached to the second surface of
the patterned layer by means of anodic bonding.
7. A method according to claim 1, wherein, in the step of removing
the supporting substrate and the intermediate layer, the supporting
substrate is removed by etching, the intermediate layer acting as
an etch stop, whereupon the etching method is changed so that the
intermediate layer is etched and the patterned layer acts as an
etch stop.
8. A method according to claim 1, wherein the fluid device is a
capillary path, the providing step including the step of selecting
a basic wafer whose patterned layer has a height of such a nature
that a fluid to be transported in the fluid structure is
transportable by capillary forces.
9. A fluid device comprising: a patterned layer with a fluid
structure, said fluid structure having an active height which
corresponds to the thickness of the patterned layer; a first
transparent wafer on a first surface of the patterned layer; and a
second transparent wafer on a second surface of the patterned
layer.
10. A fluid device according to claim 9, wherein the semiconductor
layer consists of silicon.
11. A fluid device according to claim 9, wherein the first and
second transparent wafers consist of glass and are connected to the
patterned layer by an anodic bond.
12. A fluid device according to claim 9, wherein the fluid
structure is passivated by an oxide layer.
13. A method of producing a fluid device with a fluid structure
having an active height, said method comprising the steps of:
providing a basic wafer comprising a supporting substrate, an
intermediate layer on the supporting substrate and a patterned
layer on the intermediate layer, the intermediate layer being
transparent and of such a nature that it is essentially not
impaired by a patterning of the patterned layer, and the thickness
of the patterned layer determining the active height of the fluid
structure, patterning the patterned layer so as to produce the
fluid structure of the fluid component, the fluid structure
extending from a first surface of the patterned layer to the
intermediate layer; attaching a first transparent wafer so that the
fluid structure is covered; removing the supporting substrate so
that the transparent intermediate layer is exposed; and attaching a
second transparent wafer to the intermediate layer.
14. A fluid device comprising: a patterned layer with a fluid
structure, said fluid structure having an active height which
corresponds to the thickness of the patterned layer; a first
transparent wafer on a first surface of the patterned layer; a
transparent intermediate layer on the other surface of the
patterned layer; and a second transparent wafer on said transparent
intermediate layer.
15. An analysis apparatus comprising: a fluid device comprising: a
patterned layer with a fluid structure, said fluid structure having
an active height which corresponds to the thickness of the
patterned layer; a first transparent wafer on a first surface of
the patterned layer; and a second transparent wafer on a second
surface of the patterned layer or, alternatively, on a transparent
intermediate layer arranged between the second wafer and the second
surface of the patterned layer; a sample fluid being arranged in
said fluid component; a light source for transmitting light onto
the first transparent wafer of the fluid component; a light
detector for detecting light that emerges from the second
transparent wafer of the fluid component; and a sample fluid
analyzer for determining a property of the sample fluid making use
of the light emitted by the light source and detected by the light
detector.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to analytics and in particular
to fluid devices which are suitable for analytic applications.
BACKGROUND OF THE INVENTION AND PRIOR ART
[0002] In the field of analytics there is a great demand for fluid
devices and in particular capillary paths for transporting e.g.
fluids by means of capillary forces, for examining them while they
are being transported or for producing sample receptacles in which
the fluids stand and the surfaces of which are treated with
chemical substances so that specific sample fluids will undergo a
reaction with these substances, said reaction causing e.g. a change
in colour of these sample fluids. In order to be able to detect
such a change in colour of a sample fluid, or in order to be able
to detect the optical properties of a sample fluid in general, it
is important that fluid devices are transparent on both sides so
that analyses can be carried out in transmitted light, e.g. by
making use of fluorescent properties.
[0003] Capillary paths are nowadays used in a great variety of
technical fields, e.g. in the field of chemical analytics and
biochemistry. Such capillaries are etched into silicon wafers and
then provided with a cover and thus closed. Although a glass cover
can be used for closing such silicon-etched wafers, a substrate
wafer, which is normally not optically transparent, is provided on
the back, i.e. on the other side of the capillary path. Hence, such
capillary paths are not suitable for transmitted-light analyses. In
order to be actually able to carry out optical analyses with such
capillary paths, it is necessary to apply e.g. a metal layer to the
silicon-etched fluid structures, so that a reflection analysis can
be carried out. In addition to the fact that such capillary paths
are not suitable for transmitted-light determinations, the
application of a mirror coating to the silicon is a further
production step, which is complicated and which increases the costs
for the fluid device.
[0004] In addition, it is difficult to adjust precise depths of the
fluid structure by means of etching methods. It is true that very
precisely controllable amounts of material can be removed by
dry-etching techniques, but these techniques are disadvantageous
insofar as the etching parameters must be controlled very
precisely; this, in turn, results in high production costs for such
capillary components. If the etching parameters are not strictly
controlled in this way, a high reject rate will occur in the
production process.
[0005] Especially in the field of analytics, disposable analysis
elements are used to an increasing extent. Hence, fluid devices
become more and more mass-produced articles. Especially
mass-produced articles should fulfil the requirement of being
economy-priced. It follows that even small differences in prices
will have the effect that one product will gain more acceptance on
the market than another. Only economy-priced fluid devices are
therefore competitive.
SUMMARY OF THE INVENTION
[0006] It is the object of the present invention to provide an
economy-priced method for producing a fluid device, and
economy-priced fluid device and an economy-priced analysis
apparatus.
[0007] In accordance with a first aspect of the invention, this
object is achieved by a method of producing a fluid device with a
fluid structure having an active height, said method comprising the
following steps: providing a basic wafer comprising a supporting
substrate, an intermediate layer on the supporting substrate and a
patterned layer on the supporting substrate, the thickness of the
patterned layer determining the active height of the fluid
structure, said intermediate layer being of such a nature that it
is essentially not impaired by a patterning of the patterned layer;
patterning the patterned layer so as to produce the fluid structure
of the fluid device, the fluid structure extending from a first
surface of the patterned layer to the intermediate layer; attaching
a first transparent wafer so that the fluid structure is covered;
removing the supporting substrate and the intermediate layer so
that the fluid structure is exposed at a second surface of the
patterned layer; and attaching a second transparent wafer so that
the fluid structure is covered.
[0008] In accordance with a second aspect of the invention, this
object is achieved by a fluid device comprising: a patterned layer
with a fluid structure, said fluid structure having an active
height which corresponds to the thickness of the patterned layer; a
first transparent wafer on a first surface of the patterned layer;
and a second transparent wafer on a second surface of the patterned
layer.
[0009] In accordance with a third aspect of the invention, this
object is achieved by a method of producing a fluid device with a
fluid structure having an active height, said method comprising the
steps of: providing a basic wafer comprising a supporting
substrate, an intermediate layer on the supporting substrate and a
patterned layer on the intermediate layer, the intermediate layer
being transparent and of such a nature that it is essentially not
impaired by a patterning of the patterned layer, and the thickness
of the patterned layer determining the active height of the fluid
structure; patterning the patterned layer so as to produce the
fluid structure of the fluid component, the fluid structure
extending from a first surface of the patterned layer to the
intermediate layer; attaching a first transparent wafer so that the
fluid structure is covered; removing the supporting substrate so
that the transparent intermediate layer is exposed; and attaching a
second transparent wafer to the intermediate layer.
[0010] In accordance with a fourth aspect of the invention, this
object is achieved by a fluid device comprising: a patterned layer
with a fluid structure, said fluid structure having an active
height which corresponds to the thickness of the patterned layer; a
first transparent wafer on a first surface of the patterned layer;
a transparent intermediate layer on the other surface of the
patterned layer; and a second transparent wafer on said transparent
intermediate layer.
[0011] In accordance with a fifth aspect of the invention, this
object is achieved by an analysis apparatus comprising: a fluid
device including a patterned layer with a fluid structure, said
fluid structure having an active height which corresponds to the
thickness of the patterned layer; a first transparent wafer on a
first surface of the patterned layer; and a second transparent
wafer on a second surface of the patterned layer or, alternatively,
on a transparent intermediate layer arranged between the second
wafer and the second surface of the patterned layer; a sample fluid
being arranged in said fluid component; a light source for
transmitting light onto the first transparent wafer of the fluid
component; a light detector for detecting light that emerges from
the second transparent wafer of the fluid component; and a sample
fluid analyzer for determining a property of the sample fluid
making use of the light emitted by the light source and detected by
the light detector. The present invention is based on the finding
that, for producing a fluid device, a basic wafer is used, which
comprises a supporting substrate, an intermediate layer on the
supporting substrate and a patterned layer on the supporting
substrate, the thickness of the patterned layer determining the
active height of the fluid structure of the fluid device. Such
basic wafers, which may e.g. be SOI wafers (SOI=Silicon On
Insulator), are offered with precisely specified thicknesses of the
semiconductor layer. In the case of SOI wafers, the intermediate
layer is the insulator/oxide layer, whereas the patterned layer is
the semiconductor layer.
[0012] Such basic wafers can be produced industrially as
high-precision components. Since such basic wafers are offered by
the industry in very high numbers of pieces, their prices are
comparatively moderate, since they cannot only be used in the field
of analytics but in the whole field of electronics or
microstructure technology.
[0013] According to the present invention, the semiconductor layer
of the basic wafer, i.e. the silicon layer in the case of an SOI
wafer, is patterned so as to produce a fluid structure of the fluid
device, the fluid structure extending through the semiconductor
layer. The intermediate layer is implemented such that it is
essentially not impaired by the patterning of the patterned layer
and that--in the case of etching--it acts as an etch stop.
[0014] A transparent wafer is then applied so that the fluid
structure is covered. Following this, the basic wafer is processed
from the other side in such a way that the supporting substrate and
the insulating layer are removed. The fluid structure is re-opened
on its back in this way. Subsequently, a second transparent wafer
is attached to the exposed surface of the semiconductor layer so
that the fluid structure is covered.
[0015] If the intermediate layer is transparent, as in the case of
SiO.sub.2, it may also be retained, since it will not essentially
impair the transmitted-light analysis.
[0016] One advantage of the present invention is that a fluid
device which is transparent on both sides has now been created,
which can easily be used for transmitted-light analyses.
[0017] A further advantage of the present invention is that it is
no longer necessary to adjust the active height of the fluid
structure by very precisely controlled etching parameters, this
height being simply determined by the thickness of the
semiconductor layer. The accuracy of the active height of the fluid
structure is therefore already determined prior to the actual
production of the fluid device, viz. by the thickness of the
semiconductor layer specified by the manufacturer of the basic
wafer.
[0018] A further advantage of the present invention is that, during
the patterning of the semiconductor layer, etching methods can be
used, which need not be controlled precisely. On the contrary, the
insulating layer of the basic wafer automatically acts as an etch
stop so that a very precise active height of the fluid structure
will always be achieved independently of the etching parameters.
The only requirement to be satisfied is that the semiconductor
layer is fully etched through so as to achieve a fluid structure
having a constant height.
[0019] Still another advantage of the present invention is that
fluid devices for many different cases of use, i.e. with many
different respective active heights of the fluid structures, can be
obtained by means of the same production method by simply selecting
different basic wafers with different thicknesses of the
semiconductor layers. Since the same production method can
therefore be used for a large number of different fluid devices,
the production costs per fluid device will be reduced because even
small batches of fluid devices having different specifications can
be produced, without any complicated change-over of the production
plant being necessary after each small batch.
[0020] All this is achieved due to the fact that the decisive
parameter, viz. the active height of the fluid structure, is no
longer determined by the production process itself, but by the
starting material, viz. the basic wafer.
[0021] It follows that according to the present invention fluid
devices closed on both sides thereof with transparent wafers, e.g.
glass covers, can be produced with high accuracy. The accuracy is
no longer-determined by the production method, but by the use of
basic wafers. Due to the fact that the fluid structures are
obtained by standard semiconductor-technology process steps, it is
also possible to produce very complicated fluid structures with
arbitrary geometries on a basic wafer so that the method according
to the present invention can be used for producing not only
capillary paths but also cavities, branches, passive valves and the
like.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] In the following, preferred embodiments of the present
invention will be explained with reference to the drawings
enclosed, in which:
[0023] FIG. 1 shows a sectional view of a basic wafer after the
step of patterning the semiconductor layer;
[0024] FIG. 2 shows a sectional view through a basic wafer having a
first transparent wafer applied thereto;
[0025] FIG. 3 shows a sectional view of the basic wafer after the
removal of the supporting substrate and of the insulating layer;
and
[0026] FIG. 4 shows a sectional view of a fluid device according to
the present invention after the application of a second transparent
wafer to the back of the fluid device.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0027] FIG. 1 shows a basic wafer comprising a supporting wafer 10
having applied thereto an insulating layer 12 which is, in turn,
covered by a semiconductor layer 14. An SOI structure is preferably
used as a basic wafer, i.e. a structure in the case of which the
semiconductor layer consists of silicon, the insulating layer
consists of silicon oxide, and also the supporting wafer 10 is
produced from silicon. In FIG. 1, a fluid structure 16 is already
shown, which is preferably produced by dry etching the silicon
layer 14. As known in the field of technology, a photoresist is
applied to the semiconductor layer prior to the dry-etching step;
this photoresist is then exposed at the locations at which the
fluid structure 16 is to be created.
[0028] The present invention is also applicable to all
supporting-structure/intermediate-layer/patterned-layer systems in
the case of which the intermediate layer is of such a nature that
it is essentially not impaired by a patterning process used for
patterning the patterned layer. The height of the active pattern is
then determined by the thickness of the patterned layer alone and
is not determined by the patterning method, since the intermediate
layer is not impaired when the patterned layer is being
patterned.
[0029] The semiconductor layer is patterned such that the fluid
structure 16 extends from a first surface 18a of the silicon layer
down to a second surface 18b of the silicon layer 14. The buried
oxide layer 12 serves as stop layer for the dry-etching process and
guarantees thus a high accuracy with respect to the future height
of the fluidic structures, which is determined by the thickness of
the silicon layer d, which is specified within very exacting
tolerances by the manufacturer of the SOI wafer.
[0030] FIG. 2 shows a sectional view through the basic wafer; now
the basic wafer has, however, applied thereto a glass wafer 20
which covers the fluid structure 16. It goes without saying that,
instead of the glass wafer 20, any other transparent wafer can be
applied to the silicon layer 14. For attaching the transparent
wafer to the silicon, anodic bonding, for which glass is most
suitable, is, however, preferred.
[0031] If necessary, the fluid structure 16 can be passivated with
an oxide layer, which is designated by reference numeral 22 in FIG.
2, before it is covered by the glass wafer 20. The oxide layer 22
can, however, be omitted in cases in which it is of no importance
to the future arrangement whether or not the silicon is
passivated.
[0032] Subsequently, the supporting wafer 10 is removed from the
back by grinding, etching and the like. The oxide layer 12 serves
again as a stop layer for an etching process. Subsequently, the
oxide layer 12 can be removed so that the fluid structure 16 is so
to speak re-opened from the back. If the oxide layer is transparent
it may also be retained, that is it does not have to be
removed.
[0033] For removing the intermediate layer, which acted as an etch
stop, another etching method can be used, in the case of which the
intermediate layer is etched while the patterned layer acts as an
etch stop.
[0034] In the case of a silicon/silicon-oxide system, KOH, which
does not attack silicon oxide, can be used for etching silicon,
whereas hydrofluoric acid, which does not attack silicon, can be
used for removing the insulating layer.
[0035] Those skilled in the art know many other material systems
where two layers are provided and in the case of which one layer is
not impaired when the respective other layer is being
patterned.
[0036] This situation is shown in FIG. 3. It can be seen that by
removing the supporting substrate and the insulating layer and,
optionally, the passivation layer on the base of the fluid
structure, the second surface 18b of the fluid structure is
exposed, the active height of the fluid structure being only
determined by the thickness of the silicon layer of the SOI
structure.
[0037] FIG. 4 shows a finished fluid device having, in comparison
with FIG. 3, only a second transparent wafer 22 attached to the
second surface 18b; when silicon is used as a semiconductor layer
14, this second transparent wafer will preferably be a glass wafer
as well, since this glass wafer can advantageously be connected to
the silicon 14 by anodic bonding.
[0038] The fluid device shown in FIG. 4 is therefore characterized
in that it has a glass cover at the top and at the bottom and that
the height of the fluid structure of the fluid component, which is
designated by d in the figures, corresponds to the thickness of the
semiconductor layer 14.
[0039] Reference should be made to the fact that the terminals of
the fluidic structures to the outside can be produced either
laterally or by structuring passages in the glass wafers 20 and
22.
[0040] A preferred application of the fluid devices according to
the present invention is the use these fluid devices in combination
with an analysis apparatus operating with transmitted light. For
this purpose, a sample fluid, which is contained in the fluid
structure 16, is illuminated from above, i.e. through the first
glass wafer 20, making use of a light source. After having passed
through the second glass wafer, the light transmitted through the
sample fluid is detected by means of a light detector. A sample
fluid analyzer can then determine properties of the sample fluid
making use of the spectrum of the light transmitted into the sample
fluid and making use of the spectrum of the transmitted light.
[0041] The fluid devices according to the present invention can
advantageously be used in the fields of in vitro diagnostics or
clinical diagnostics, basic biological research, in particular
genomics, forensics, food analysis or the screening of medical
products.
[0042] For the individual cases of use, immobilized biomaterials,
such as DNA oligonucleotides, can be arranged on the surface of the
fluid structure; these immobilized biomaterials may serve as
specific interaction partners, i.e. they define functional
elements. When the fluid structure is designed such that rows and
columns are formed, the fluid devices are also referred to as
biochip arrays. Arbitrary numbers (up to several thousands) of
biochemical functional elements may be arranged.
[0043] The biomaterials can be applied to the semiconductor fluid
structure making use of various methods, e.g. by means of a
synthesis of DNA oligos directly on the matrix making use of
photolithographic masks, or by spotting synthesized oligos onto the
matrix.
[0044] According to the present invention, fluid feed materials are
conducted through the capillaries of the fluid device into the chip
in the case of the DNA array synthesis; these fluid feed materials
bond to the capillary walls due to local light activation, as
described e.g. in DE 19940750 A1. A fast, efficient and
consequently economy-priced production of biochips is achieved in
this way so that such chips can gain acceptance as mass-produced
articles. In comparison with uniform surfaces, the fluid devices
according to the present invention provide more advantageous
physiochemical properties of the flow and wetting processes in the
fluid structures, in particular if these fluid structures are
dimensioned such that they act as capillaries.
* * * * *